1. Field of the Invention
The invention relates generally to the fabrication of metal layers and interconnects for semiconductor devices and more particularly to the fabrication of modified ARC layer structures.
2. Background of the Invention
Metal layers and interconnects are important technologies in semiconductor manufacturing. Interconnects electrically connect different conductive wiring layers in a semiconductor chip. The conductor layers can be layers formed on a substrate surface, such as a source/drain contacts or gate structures, or overlaying metal wiring layers. It is important that the interconnects, vias, and conductive wiring layers be reliable, be a small as possible to miniaturize the circuits, and have wide process windows for high yields.
Often, antireflective coating (ARC) layers are formed over the metal layers and interconnects. The ARC layers, which often comprised titanium nitride anti reflective coating, are used to improve photolithographic processes by providing a dull surface overlying the reflective metal lines.
In addition to the overlaying ARC layers, metal layers are formed having underlying barriers, such as TiN, etc. Such layers are critical in helping the metal layers, which usually comprised aluminum, to adhere to various surfaces, such as oxides. The layers also block aluminum metal from spiking out and reacting with other surfaces, such as silicon. The combinations of layers is often referred to as the metal stack.
One problem that can occur when the ARC layer is too thin, e.g., <600 A, is an effect known as a crown defect. Crown defects are illustrated in FIGS. 1A through 1C. In FIG. 1A, crown defects 101 and 102 can be seen extending from metal interconnects 107. A close up view of a crown defect 103 is illustrated in FIG. 1B. FIG. 1C illustrates another crown defect 104 extending from a metal line 105.
The main cause of crown defect formation is the penetration of aqueous developer through the ARC layer onto the underlying metal layer from which metal lines, e.g. lines 105 and 107, are formed during subsequent photolithographic steps. The aqueous developers comprise strong alkaline solutions that can remove the protective metal oxide from the metal surface and enhance the metal surfaces susceptibility to galvanic corrosion, e.g. as a result of rinse water during a rework process.
Bridging is another problem that can also occur. FIG. 1A illustrates the bridging problem. Bridging occurs when a defect forms that bridges one metal line to another. Thus, in area 106 of FIG. 1A it can be seen that several bridges have formed bridging metal lines 107.
Both the problems of crown defects and bridging will reduce the yield and increase processing cost.